The overarching theme of this project is to explore the mechanisms that lead to liver inflammation/injury in obesity. We will focus on extracellular miRNAs of intestinal epithelial cells (IECs) and macrophages. Specifically, we will examine how polyunsaturated fatty acids mediated-intestinal inflammation stimulates the production of extracellular miRNAs from IECs and the consequences of these events. Novel in vitro and in vivo approaches will be used to address mechanisms of action with the goal of identifying new targets for intervention. We propose that dietary n-6 polyunsaturated fatty acids (n-6 PUFAs) promote liver inflammation and injury via IEC-derived exosomes. We specifically propose that Stat3-activated extracellular miRNAs are the key to the accumulation/polarization of macrophages in liver in obese mice. Based on our published work and other preliminary data, this proposal will test the hypothesis that the n-6 PUFAs regulate the production of extracellular miRNAs from intestinal epithelial cells through Stat3 signaling, which initiates a crosstalk among macrophages, NK cells and hepatocytes in liver. Moreover, we will determine whether diet fat-associated nanoparticles carrying miR-155 inhibitor have potential therapeutic implications in obesity. These hypotheses will be tested in the following Specific Aims: Aim 1: Determine whether IEC-derived extracellular miRNAs regulated by the n-6 PUFAs/Stat3 pathway are specific mediators of NFALD development and progression. Aim 2: Determine whether alteration of IEC miRNAs via STAT3 modulation affects the severity of HFD-induced liver inflammation and injury in obesity. Following the successful completion of the above Specific Aims, our novel studies will (i) validate Stat3-activated extracellular miRNAs is directly relevant to the accumulation/polarization of hepatic macrophages in obesity, and (ii) provide a foundation for future mechanistic investigation of the regulation of diet fat and extracellular miRNA in obesity therapy.